On golf courses, a golf flag is placed in hole cups located in a green or a practice area about 2-3 cm under the grass surface. The hole cups are about 15 cm deep, and are provided in the bottom with a boring that fits a ferrule which is mounted at the bottom of the flag stick. It is necessary that the ferrule fits tightly in the hole cup in order for the flag to stand upright. There are two reasons for which it is particularly important for the flag to stand straight up. When the ball is shot towards a hole from a certain distance, the golf player uses the flag as sighting point, and if the flag stick does not stand straight in the hole cup, the golf player will have difficulty in sighting correctly. The other reason is that when the flag stick stands skew, it may block the hole for the golf ball when shooting towards hole outside the green where the flag stands in the hole cup.
The golf flag is subjected to wind action, giving rise to two effects which reduce the durability of the ferrule and the hole cup—friction by rotation and mechanical loads between ferrule and hole cup, respectively. Wind from different directions will make the ferrule rotate in the hole cup if the friction between the two elements is not sufficient to prevent such rotation. The friction forces will wear the ferrule and the hole cup such that a play arises. The golf flag may now tilt, giving rise to additional wear. Another effect of the mentioned rotation of the ferrule in the hole cup is that the ferrule will slowly be rotated up of the hole cup. When the engagement of the ferrule in the hole cup becomes insufficient, the flag will turn over completely. Therefore, manual check of all flags on a golf course has to be performed before each day of playing in order to ensure that all flags are standing in their hole cup.
To this is added influence from common use which consists of taking the flag up and putting it down in the hole cup each time a player reaches the green. The ferrule and the centre hole in the hole cup will thus be gradually worn, whereby the fit between the two elements becomes more and more loose. The golf flag may thereby be tilted with deflections that are gradually increased, which by itself will accelerate the wear. The position of the hole cup under the ground surface will furthermore entail that sand and soil may come into the hole cup and its centre hole, further accelerating the above process. At some point, the size of the mentioned deflections occurring when the golf flag tilts will be unacceptable, and the golf flag has to be replaced.
U.S. Pat. No. 4,114,879 discloses a solution where the lowermost part of the ferrule is a cylinder provided with two collars. According to the disclosure, these collars have an anchoring effect against the wind action such that the flag retains its upright position. The disadvantage of this embodiment is that the collars will be worn rapidly as the wearing faces are becoming smaller. Moreover, there is a clearance between the ferrule and the hole cup opposite the lower collar, as this collar has smaller diameter, why sand grains may appear between the collar and the hole cup, contributing to additional wear. The ferrule will thus rapidly loose its straightening effect.